Look stamped in the front frame rail, left side. Many years ago when I had a T-bucket, Total Performance stamped their manufacturing number there.

If you do have a clear title, then you can buy an after market data plate from many folks like MAC's, Snyder's or any other that sells repro materials. Stamp the correct number on it and you should be golden. This is the p/n for a '33: 40-14002. I would probably use an 'A' version tho as it is 'cleaner': Search Within MAC's Antique Auto Parts. All you are worried about are matching numbers, not style (if you have that clear title)